Posted
by
Soulskill
on Friday January 04, 2013 @05:41PM
from the keep-bruce-willis-on-hand-just-in-case dept.

Zothecula writes "To paraphrase an old saying, if the astronaut can't go to the asteroid, then the asteroid must come to the astronaut. In a study released by the Keck Institute for Space Studies, researchers outlined a mission (PDF) to tow an asteroid into lunar orbit by 2025 using ion propulsion and a really big bag. The idea is to bring an asteroid close to Earth for easy study and visits by astronauts without the hazards and expense of a deep space mission. Now, Keck researchers say NASA officials are evaluating the plan to see whether it's something they want to do. The total cost is estimated to be roughly $2.6 billion."

I think that would depend highly upon the composition of the asteroid they capture.

Being scientists, and only getting big bucks on the table for a one shot deal, I would bet on their choosing as heterogenous of an asteroid as possible, preferably one with clear signs of stratification.

This way portions of the asteroid will be rocky, while others will be more iron based, allowing for the greatest possible dataset to be collected from the expense.

Such an asteroid would almost certainly fragment on re-entry, should it fall from orbit. This means many smaller asteroids, instead of a monolithic 500,000kg bombshell. I would expect most of it to burn up, and for it to rain tiny particles over a large area, with a considerable chance it will hit ocean.

From Wikipedia. [wikipedia.org] "It has been estimated that all the gold mined by the end of 2009 totaled 165,000 tonnes. At a price of US$1900 per troy ounce, reached in September 2011, one tonne of gold has a value of approximately US$61.1 million. The total value of all gold ever mined would exceed US$10.1 trillion at that valuation."

So the gold asteroid weighs 500 tonnes. That, by the way, is about what the European Central Bank has on hand. By my calculation (don't trust it) that's 0.3 percent of all the gold ever

Forgive me if I'm wrong, but how could this possibly be a bad thing? First, I doubt that 500,000 kilograms would actually collapse the precious status of gold catastrophically; there's a lot of gold out there, a lot of obsession and history with valuing it greatly, and frankly the powers that be would probably, as is done with diamonds, lock the "excess" in vaults and release slowly, over time.

But presuming America called "BS" and demanded disbursement, and gold prices suffered serious devaluation, we coul

Have you considered the possibility that they're not idiots? If it's 7m diameter asteroids, I assume those are small enough to burn up in our atmosphere. Either way, what are the chances that your thoroughly researched and calculated concerns will be something they haven't considered or justifiably dismissed?

But wait the moron scientist will calculate it as 7 miles diameter instead of 7 meters and we'll all die to some math screwup...

Precedent

"The Mars Climate Orbiter, which cost $Aus 136 million, disappeared because a Lockheed Martin engineering team used Imperial measurements while the JPL (Jet Propulsion Lab) team used the more conventional metric system. The wrong navigation information was sent to the Mars Climate Orbiter. It most likely burnt up in the atmosphere."

Here's another fucking precedent: the same agency landed people on the Moon with computers no more powerful than that of a pocket calculator. And this same agency explored all of the gas giants and has sent probes to every single planet, including multiple landings on Mars.

Sorry, but one screwup by NASA doesn't obliterate their astounding exploration record. Nobody, but nobody can even compare. There is no better agency in the world that could pull off this mission.

The question is perfectly reasonable for anyone on earth to ask. This idea that you can't ask rocket scientists to justify anything is pretty elitist [cnn.com] if you ask me.

How precisely can the place it in orbit. You've got something on the order of 417 metric tons of material (if measured on earth) assuming its a loosely packed ball of rock, which many asteroids of that size are. That could do a lot of damage if it became uncontrolled.

Can you bag that without it changing shape?Can the bag and tethers withstand the amount of strain necessary to decelerate it from its current orbit to earth orbit, then to the moon's orbit?Can the engine last that long?What happens when (not if) the engine fails?Would it burn up on entry into earth's atmosphere if the engine failed, or a tether broke?If you lose control of the package for any reason, where does it end up? In 5 years, in 25 years?

If you, and they are so certain of their calculations and abilities, why not put it in earth orbit as others have suggested?

You can ask questions, but you can also answer them. For example, it doesn't take a lot of research to find out that Earth routinely gets hit by objects of this size. Cities don't make up a huge portion of the Earth's surface area, but if asteroids of this size were cratering the Earth, we'd have noticed it by now.

Sorry to reply to my own post - I mistook the energy in 1 ton of TNT (4.2e9 Joules) as being the energy for 1 kiloton of TNT, so my energy estimate is 1000x too large. Actual energy release would be in the low kiloton range, which I agree we could easily miss if most of the energy were coupled to the atmosphere by an endoatmospheric burst.

The asteroid's delta vee relative to Earth would be very low by the time it was approaching the neighborhood. That is strictly implied by the idea of "capturing" it. As such it would present very little more danger to the Earth than Sky Lab did. Not pleasant, but not a dinosaur killer, either.

The Tunguska Event may have been an asteroid with a high delta vee. It may have been something else. It was not an asteroid cozying up slowly to the Earth, the way a captured asteroid would.

* Energy before atmospheric entry: 1.63 x 1013 Joules = 0.39 x 10-2 MegaTons TNT* The average interval between impacts of this size somewhere on Earth is 1.9 years* The projectile begins to breakup at an altitude of 65500 meters = 215000 ft* The projectile bursts into a cloud of fragments at an altitude of 41400 meters = 136000 ft* No crater is formed, although large fragments may strike the surface.* The air blast at this location [1 km away from the impact point] would not be noticed. (The overpressure is less than 1 Pa).

No, we wouldn't. Tunguska was roughly 10m in diameter. Additionally orbiting the moon it's relative speed would be lower, so it'd have less energy if hitting the earth.

Nobody has any real clue exactly how big Tunguska was [crystalinks.com], because at the time that estimate was done nobody had any clear idea of the composition of asteroids or other rogue rocky bodies. Further, Tunguska is thought to have been an air burst, rather than a single penetrator, and some estimates have it as big as 20 meters. Has it hit any large metropolitan area it would have been the single largest disaster to humans on earth.

It is actually staggeringly hard to deorbit an asteroid into a planet. Things don't just "fall' towards gravity wells - they orbit them. To actually hit something, you need to remove all the lateral motion relative to the body - which involves a lot of applied delta-V in the right direction of the orbit - for it to actually fall towards the target (+ - whatever you can get away with if you want to just skim the atmosphere).

Without intentionally trying to, we're likely to have hundreds of years warning if an asteroid relocation was going to hit us.

That got me thinking about something from 3001 (not that good a read, but still) wherein humans had been dropping comets onto Venus to slow terraform it. I wonder how many we'd have to drop onto Mars to make it a little more liveable there...

For mars? Better take archemedes up on his really big lever and fulcrum offer:

Mars has an erratic axial tilt that needs correcting. That needs a big assed moon. A good candidate is Vesta.

Mars is also only about 2/3 the mass of earth. For stable tectonic activity, you need to rain 1/3 of an earth on it.

Then, after cooking, you need to wait for it to cool off. Dropping that much material on mars will heat the crust up to molten temps. (And likely also change the length of year, and length of day.) So, regardl

Dropping asteroids on mars gives us material on the surface for building.

Terra forming would require restarted the core.

Now, create a giant umbrella between mars and the sun the blocks certain spectrum while focusing the rest might help with that.Bio- engineering Venus does not pose a less daunting time table.,. I's just a different set of problem on a different planet.And we could do both.

Mars already has a large extant of iron and oxygen on its surface. It is why it is red. (Iron III oxide.)

For venus, I could see it dropping to "still bitching hot, but cool enough to work with on the surface with robots" in about 2000 years.

Venus' surface temp is just a few degrees centigrade below the thermal decomposition temperature of aramid plastics. (Related to kevlar and pals.) Venus has a similar overall quantity of nitrogen in its atmosphere as earth does, just diluted by considerable excess of carbon dioxide.

The secret to venus is to sequester the carbon.

Engineering an extremophile atmospheric microbe to colonize the tops of the sulfuric acid cloud layer (were it's a nice, sunny 70F or so, at earth sealevel pressures.) That uses a stable sulfur cycle based derivitive of photosynthesis, that is engineered to produce aramid plastics, would do just that.

Lacking any natural predators, and having a huge petri dish to colonize, with an excess of "food", the little bitches would rapidly "snow" out thermally stable plastic molecules and deplete the carbon dioxide in the atmosphere, and thereby puncture the thermal equilibrium of the planet.

The issue is the hydrogen scarcity. The microbes would have to be able to produce their own water from their sulfur based respiration cycle from sulfuric acid, excrete sulfur dioxide, and sequester the water inside their cellular membranes. This means they would have to be extraordinarily robust in the face of anhydrous sulfuric acid. That alone is a pretty impressive feat to accomplish with engineered biology. I was thinking that the microbes could use a heavy metal complex with lead to reduce the chemical activity of their cellular membranes, and use of the aramid plastic as internal skeletal structures might work. (One of the interesting features on venus is lead sulfide snow. It volatizes on the surface, then crystalizes in the atmosphere. This makes it a potential raw material for the microbes to use. Lead is very resistant to acidic attack.)

Releasing such microbes on venus would cause a runaway reaction in the atmosphere, transforming venus from a cloudy hot furnace, into a hellish sea of acidic gel oceans, and do so very quickly.

Venus has a similar overall quantity of nitrogen in its atmosphere as earth does, just diluted by considerable excess of carbon dioxide.

Are you sure about that? I know Venus's atmosphere is much denser but it's 98% CO2, is it really that dense that 3/4 of the Earth's atmosphere would fit into the remaining 2%? Your right, the hardest problem is lack of Hydrogen caused by a runaway greenhouse effect that evaporated the Venusian oceans, the same fate awaits Earth in about half a billion years from now ( much sooner if we burn all the coal as per current plans). We can already terraform planets, we have been doing so on a significant scale rig

I know Venus's atmosphere is much denser but it's 98% CO2, is it really that dense that 3/4 of the Earth's atmosphere would fit into the remaining 2%?

Oh yes, 80 atmospheres of pressure at the Venus surface and it has pretty close to the same gravity profile (a bit less gravitational pull) as Earth does.

Your right, the hardest problem is lack of Hydrogen caused by a runaway greenhouse effect that evaporated the Venusian oceans, the same fate awaits Earth in about half a billion years from now ( much sooner if we burn all the coal as per current plans).

Not at all. There's two things to keep in mind. First, there isn't enough carbon in fossil fuels to do this thing. And even if there was, there isn't enough oxygen. There is probably enough fossil fuels, if one could somehow extract and burn it, to turn the Earth's atmosphere toxic to current human life. But that only takes about 5000 parts per million (0.

It would be spectacular if movies were made based upon potential Nasa missions and the awesome adventures that would entail. Perhaps that would get through to the masses. Unfortunately these thins are so mind-boggling to our uneducated masses that they don't see the amazing technical feat and engineering this requires, nor the art and wonder of it all. It's beyond their culture of lulz, shopping, and life stress. We love our movies though and they can still help us remember how to dream. I'd love to see a resurgence of sci-fi with an aim at inspiring us to push forward.

It would be spectacular if movies were made based upon potential Nasa missions...

If you ignore the part about the monoliths, 2010 is quite good in this respect. Personally, I've always thought that a film set during the Belters' secession from Earth (as in Larry Niven) could make for very interesting sci-fi while still sitting at the 'hard' end of the spectrum.

It'd be cooler if it visually simulated an asteroid of a user-entered size hitting the earth, and showing the impact visually instead of always using stock cgi footage of an asteroid entering the atmosphere and then just showing the raw data.

NASA should copyright the story leading up to, including, and after the lassoing. They could then sell the stories to the film industry and merchandise like crazy to recoup some of the costs. To add a bit of color, they should recruit astronauts with dark pasts, a drinking problem, or who are Elmo.

For those who don't want to take the time to put in the numbers.
No crater would be formed should it hit the earth although maybe some small chunks might land. If it hit the oceans nothing would happen. Something this size (7 meters) hits the earth every 2 years or so.

Billy: You see those two rocks? Asteroids. I was an engineer working on them. First they just wanted to put one but I said, "Fellas, we're here. What the hell, throw the other one up". Turned out pretty well, didn't it?Henry: Fantasy.

Didn't we have this story a week or so ago? Then NASA wasn't actually commenting on the plan... Is the news now that they actually are considering the plan? Or is it that we're talking ion thruster now rather than Atlas-v?

According to a report prepared by NASA and California Institute of Technology (Caltech) scientists, an, 'asteroid capture capsule' would be attached to an old Atlas V rocket and directed towards the asteroid between the earth and the moon. Once close, the asteroid capsule would

I don't really see the point of astronauts visiting a rock that's smaller than they are. This is a waste of resources, there are plenty of small asteroids that come to Earth by themselves, why not study them?

Not likely. At 1 meter distance, it could attract pebble-sized debris in around 8 hours. But at 10 meters, it would take a year to collect the same debris, and at 1 km, it would take ten thousand centuries. (All based on my primitive physics skills; YkmMV).

Oh who cars if it costs 1000 billion per year. All that money is spent on wages that go to people who spend and support their local industries. Materials are cheap.

I'll tell you how to build a city on the moon, do it like nature uses dna to make trees or coral. Make 4 types of robots, that can mine the moon, melt regolith, shape it to sheets or blocks like lego. Then have 100000 little spi

both based on the premise of a manned Grand Tour of the solar system.Defying Gravity, being a Hollywood project revolved around aliens. Space Odyssey was done as a mockumentary and looked quite plausible.

Ok, so once the asteroid collector has delivered the asteroid to high lunar orbit, what does the spacecraft do then?

Well, if its got even a tiny fraction of its propellant left over (remember it just towed something maybe 100x its size clear across the solar system) , it slowly spirals down to low earth orbit and... REFUELS.

Now here's where things get interesting. Once it's refueled (remember its main consumable is up to 12,000 lbs. of Xenon, it gets its energy from solar power), it can do any number of things. Of course it could be sent out again to get another asteroid (including, as I mentioned in a previous post, one with precious WATER) but that might be boring. How about having it PAY FOR ITSELF by moving satellites from LEO to geosynchronous orbit. (This is very expensive as it typically requires an additional booster, I think the cost per pound is at least double that to low orbit). I think this market is on the order of $5B per year.

The reason why this would work is because the asteroid tug would clearly be capable of moving very(!) large payloads. It wouldn't even have to be very slow, if it can accelerate a 500 ton asteroid at 1/10,000th of a g, it could accelerate a 5 ton satellite at say 1/200th of a gee (taking into account the tug's own weight). So it could deliver the satellites in weeks if not days. Of course there would need to be a few minor design modifications to the tug. The collapsible "bag" would have to be removable and some sort of industry standard docking ports added. There would need to be some provision for refueling ports and critical components (gyroscopes, reaction wheels, electronics) would need to be replaceable/upgradeable like the Hubble space telescope. Of course servicing this "space tug" in this way is probably beyond the near term capabilities of robotics. Rather than this being a problem, it could be an opportunity -

- for the International Space Station to actually be USEFUL. Here it could serve as a fuel depot, servicing "garage" and interchange point for these "space tugs". The kind of problem that robotics can't handle yet are ideally suited for an astronaut with a wrench (and maybe some elbow grease). The fact that the main propellant for these tugs is Xenon, an inert noble element, makes handling the fuel much less problematic (no problems with corrosion or toxicity) and safer (no fear of explosive combustion). Even the fact that these tugs use ion thrusters would be an advantage meaning that everything would be happening very slowly, if one went out of control they could probably move the entire station out of the way (like they do when avoiding space junk). The station could also keep spare, interchangeable parts for these tugs such as additional "bags" or robot arms or other modules. In short, the ISS would have a PURPOSE.

With even a little thought, these space tugs have lots of additional uses. The same high power ion engines that can move a 500 ton asteroid could also send 500 tons of cargo cheaply (if slowly) to Mars. The same collapsible bag that can capture a tumbling asteroid can easily capture a much lighter piece of space junk. All it takes is for a government with foresight to make the initial investment that may (as I've suggested) quickly repay itself perhaps many times over. And isn't that the purpose of government (if not NASA)?

They're talking about capturing a 7-meter asteroid. Those already impact the earth roughly once every two years. And when I say "impact", I mean "break up in the atmosphere and do little to no damage to things on the ground".